Actually he didn't say it. He said, that they regained control over some territoties near Krasnogorlovka.
It depends on your definition of the term 'Russia'. As well as Canada is a part of America (as geographic term) it's not a part of the United States of America (at least not yet). Same way, Donetsk and Lugansk People Republics are parts of Russia (as cultural and linguistic space) they were not parts of the Russian Federation back in 2014. From the Kievan point of view - those were separatists.
After the 'Revolution of dignity' in Kiev (aka 'illegal Maidan Coup'), ruled by Ukrainian Neo-Nazies, there was an anti-Nazi and pro-Russian rebellion in Russian speaking South-Eastern regions of Ukraine. It was totally successful in Crimea and Sevastopol, who rejoined with the Russian Federation almost without bloodshed, partially successful in Donbass region (where Donetsk and Lugansk regions declared and de facto gained independence, backed by the Russia, like Taiwan is backed by the USA) and was cruelly supressed in Odessa, Kharkov, Dnipropetrovsk and other regions (google Odessa Massacre 2014). There was a stalemate situation in Donbass region between 2014-2022 - Ukraine was not able to crush defence of the rebellious Donbass Republics , and Russian Federation didn't want to start bigger war (because of potential economic problems).
Trump Administration had been keeping the situation more or less balanced, because the USA was not interested in the bigger war.
Then, Baiden (highly likely because of his family's economic interests) disbalanced the situation, encouraged the Kievan regime to attack those Donbass republics. In the last attempt to prevent the war, Russian Federation recognized independence of DPR and LPR and signed a mutual defence agreement with them. Then, Ukraine attacked DPR and LPR ("separatist regions" from the Kievan point of view, and "independent states and allies of Russian Federation" from the Moscow's point of view), what was equal (from Moscow point of view) to the direct attack against Russian Federation itself, and the Russian Federation started the Special Military operation with the limited goals of demilitarisation and denazification of Ukraine. Biden administration didn't agree that this Russian goals are legitimate, and increased support of Kieavan regime. And here we are now, at the brink of a nuclear war.